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To help cities plan for roads, transit, buildings, sidewalks, and future technologies, transportation and urban planners try to understand the movements of people between households and businesses today and in future scenarios.

When planners quantitatively prioritize transit investments, they can use either accessibility measures or ridership measures, or some combination of the two. Accessibility calculators count how easily people are able to reach opportunities (e.g. jobs) by transit, and ridership models attempt to forecast likely passengers. Historically, agencies have used both methods for different tasks, though recent criticism of ridership models coupled with the availability of new web-based accessibility calculators has made a comparison of each method important for planners to understand.

As part of Transportation Camp DC 2018, we challenged Conveyal to debate the strengths of accessibility calculators, and Anson Stewart came forward. I defended ridership models. During the debate, we showed off Conveyal's Analysis software as well as gave the first demonstration of CityCast, our web-based travel demand model that estimates ridership.